Vehicles having at least four drive wheels, also known as off-road vehicles, are designed to overcome all kinds of obstacles and, for this purpose, offer a drive system adapted to the driving conditions of the vehicle. When the vehicle is in off-road mode, the driving conditions of the vehicle are very limiting and the speed of the vehicle is accordingly low or medium.
When the vehicle is also designed for road use, it is advantageous for the driver to be able to choose between at least two, or even three, modes of operation, which can for example be a mode of operation with a single drive wheel set, a mode of operation for road with at least two drive wheel sets in which the ratio between the torque transmitted to the front wheel set and the torque transmitted to the rear wheel set varies as a function of parameters representative of the on-road behavior of the vehicle (for example speed of the vehicle, speed of the wheels, position of the accelerator pedal, angle of the steering wheel, yaw angular speed of the vehicle) in order to establish a compromise between the stability of the vehicle and the fuel consumption, and an off-road mode of operation favoring the adherence of the vehicle to the ground at low speed.
In order to allow the driver to choose a mode of operation, the vehicle may be equipped with a selector switch with several positions.
In the document EP 1 188 596, a vehicle is described that is equipped with a selector switch with three positions delivering three separate signals corresponding to a mode of operation with two drive wheels, an automatic on-road mode of operation with four drive wheels and a locked mode of operation with four drive wheels or off-road mode. When the driver attempts to activate the off-road mode at too high a speed, this mode is inhibited and the control remains in the on-road mode with four drive wheels.